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The Focusing Detector of Internally Reflected Cherenkov light (FDIRC) has been designed to separate efficiently kaons from pions up to a few GeV/c in the barrel region of a HEP experiment. This ring-imaging Cherenkov detector is based on the same principle as the BABAR DIRC, which was successfully operated at the SLAC PEP-II asymmetric B-Factory during a decade. Charged particles cross thin quartz bars in which they radiate Cherenkov light; part of these photons are trapped in the radiators by total internal reflection and propagate until a camera where they are detected by photon detectors. The FDIRC was intended for the SuperB detector, a new generation flavour factory which has been cancelled at the end of 2012 due to lack of funding. Therefore, it has been designed to be able to operate at very high luminosity (10^36/cm^2/s) and la...
The FDIRC (Focusing Detector of Internally Reflected Cherenkov light) is a charged particle identification (PID) detector which separates efficiently kaons from pions up to a few GeV/c. It is the successor of the BaBar DIRC, which was successfully operated at the PEP-II B-Factory during a decade, and benefits from the knowledge accumulated with a first focusing DIRC prototype, built and operated at SLAC in the recent years. The FDIRC is a ring-imaging Cherenkov detector based on the same concept as the BaBar DIRC. Yet, its design has been significantly improved to be able to operate at much higher luminosity (10^36 cm^-2s^-1) and with larger backgrounds. Indeed, the FDIRC was intended to cover the barrel region of the SuperB detector, a new generation flavour factory cancelled at the end of 2012 due to lack of funding. The FDIRC photon...
The FDIRC (Focusing Detector of Internally Reflected Cherenkov light) is a new concept of PID (Particle IDentification) detector aimed at separating kaons from pions up to a few GeV/c. It is the successor of the BaBar DIRC and benefits from the knowledge accumulated with a first FDIRC prototype built and operated at SLAC. The FDIRC is intended to be used in an environment with a luminosity 100 times higher than for BaBar and Belle. Backgrounds will be higher as well; yet, the FDIRC has been designed to perform at least as well as the View the BaBar DIRC. The main improvement is a complete redesign of the photon camera, moving from a huge tank of ultra-pure water to much smaller focusing cameras with solid fused-silica optics. Furthermore, the detection chain will be 10 times faster than in BaBar to reject more background and to measure...
We present results from a novel Cherenkov imaging detector called the Focusing DIRC (FDIRC). This detector was designed as a prototype of the particle identification system for the SuperB experiment, and comprises 1/12 of the SuperB barrel azimuthal coverage with partial electronics implementation. The prototype was tested in the SLAC Cosmic Ray Telescope (CRT) which provides 3-D muon tracking with an angular resolution of ~1.5 mrad, track position resolution of 5-6 mm, start time resolution of 70 ps, and a muon low-energy cutoff of ~2 GeV provided by an iron range stack. The quartz focusing photon camera couples to a full-size BaBar DIRC bar box and is read out by 12 Hamamatsu H8500 MaPMTs providing 768 pixels. We used IRS2 waveform digitizing electronics to read out the MaPMTs. We present several results from our on-going development...
We present a measurement of the $CP$-violating weak mixing phase $\phi_s$ using the decay $\bar{B}^{0}_{s}\to D_{s}^{+}D_{s}^{-}$ in a data sample corresponding to $3.0$ fb$^{-1}$ of integrated luminosity collected with the LHCb detector in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. An analysis of the time evolution of the system, which does not constrain $|\lambda|=1$ to allow for the presence of $CP$ violation in decay, yields $\phi_s = 0.02 \pm 0.17$ (stat) $\pm 0.02$ (syst) rad, $|\lambda| = 0.91^{+0.18}_{-0.15}$ (stat) $\pm0.02$ (syst). This result is consistent with the Standard Model expectation.
We present a progress status of a new concept of PID detector called FDIRC, intended to be used at the SuperB experiment, which requires π/K separation up to a few GeV/c. The new photon camera is made of the solid fused-silica optics with a volume 25× smaller and speed increased by a factor of 10 compared to the BaBar DIRC, and therefore will be much less sensitive to electromagnetic and neutron background.
A measurement of the decay time dependent $CP$-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented, along with measurements of the $T$-odd triple-product asymmetries. In this decay channel, the $CP$-violating weak phase arises from the interference between $B_s^0$-$\overline{B}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0\, fb^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 \to \phi\phi$ decays is obtained. The $CP$-violating phase is measured to be ${\phi_s =-0.17\pm0.15\mathrm{\,(stat)}\pm0.03\mathrm{\,(syst)}}$ rad. The triple-product asymmetries are measured to be ${A_U=-0.003\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$ and ${A_V=-0.017\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{...
Using the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> \pi^+\pi^- decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2\beta_s. Results from an extended approach, which uses additional inputs on B^0 -> \pi^0\pi^0 and B^+ -> \pi^+\pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value \gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2\beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effec...
A measurement of the inclusive $W \to \mu\nu$ production cross-section using data from $pp$ collisions at a centre-of-mass energy of $\sqrt{s} = 7 {\rm \, TeV}$ is presented. The analysis is based on an integrated luminosity of about $1.0 {\rm \, fb}^{-1}$ recorded with the LHCb detector. Results are reported for muons with a transverse momentum greater than $20 {\rm \, Ge\kern -0.1em V\!/}c$ and pseudorapidity between 2.0 and 4.5. The $W^{+}$ and $W^{-}$ production cross-sections are measured to be $$\sigma_{W^{+} \to \mu^{+}\nu} = 861.0 \pm 2.0 \pm 11.2 \pm 14.7 {\rm \, pb},$$ $$\sigma_{W^{-} \to \mu^{-}\overline{\nu}} = 675.8 \pm 1.9 \pm 8.8 \pm 11.6 {\rm \, pb},$$ where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity determination. Cross-section ratios and differential distribut...
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